Obama says Trump unfit to serve as US president

WASHINGTON, Aug 2 (Reuters) - President Barack Obama issued a scathing attack of Donald Trump on Tuesday for criticizing a Muslim family whose U.S. Army captain son was killed in Iraq, and he challenged Republican leaders to withdraw support for their "unfit" nominee.

Obama's comments added to a growing number of statements from Republicans and Democrats lambasting Trump for his criticism of Khizr and Ghazala Khan, who appeared at the Democratic National Convention last week.

Trump questioned whether Mrs. Khan did not speak at the convention because she was prevented from doing so by her religion and he characterized Mr. Khan's criticism of him as "vicious."

Families who lose sons or daughters who serve in the U.S. military are called Gold Star families.

"The notion that he would attack a Gold Star family that had made such extraordinary sacrifices on behalf or our country, the fact that he doesn't appear to have basic knowledge around critical issues in Europe, in the Middle East, in Asia means that he's woefully unprepared to do this job," Obama said of Trump during a White House news conference.

The Democratic president noted that leading Republicans, including Speaker of the House of Representatives Paul Ryan, Senate Republican leader Mitch McConnell, and one-time Republican presidential nominee John McCain, a U.S. senator from Arizona, had criticized Trump for his remarks but have stood by their endorsements of him.

"The question I think that they have to ask themselves is, if you are repeatedly having to say in very strong terms that what he has said is unacceptable, why are you still endorsing him?" Obama said.

"What does this say about your party that this is your standard-bearer?" Obama said.

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U.S. Republican Presidential Nominee Donald Trump arrives onstage at the Republican National Convention in Cleveland, Ohio, U.S. July 21, 2016. REUTERS/Rick Wilking

U.S. Republican presidential nominee Donald Trump is greeted by Ivanka Trump after his introduction at the Republican National Convention in Cleveland, Ohio, U.S. July 21, 2016. REUTERS/Jim Young

CLEVELAND, OH - JULY 21: Republican presidential candidate Donald Trump gives two thumbs up to the crowd during the evening session on the fourth day of the Republican National Convention on July 21, 2016 at the Quicken Loans Arena in Cleveland, Ohio. Republican presidential candidate Donald Trump received the number of votes needed to secure the party's nomination. An estimated 50,000 people are expected in Cleveland, including hundreds of protesters and members of the media. The four-day Republican National Convention kicked off on July 18. (Photo by Joe Raedle/Getty Images)

CLEVELAND, OH - JULY 21: Republican presidential candidate Donald Trump acknowledges the crowd during the evening session on the fourth day of the Republican National Convention on July 21, 2016 at the Quicken Loans Arena in Cleveland, Ohio. Republican presidential candidate Donald Trump received the number of votes needed to secure the party's nomination. An estimated 50,000 people are expected in Cleveland, including hundreds of protesters and members of the media. The four-day Republican National Convention kicked off on July 18. (Photo by Joe Raedle/Getty Images)

CLEVELAND, OH - JULY 21: Republican presidential candidate Donald Trump delivers a speech during the evening session on the fourth day of the Republican National Convention on July 21, 2016 at the Quicken Loans Arena in Cleveland, Ohio. Republican presidential candidate Donald Trump received the number of votes needed to secure the party's nomination. An estimated 50,000 people are expected in Cleveland, including hundreds of protesters and members of the media. The four-day Republican National Convention kicked off on July 18. (Photo by Win McNamee/Getty Images)

Donald Trump, 2016 Republican presidential nominee, speaks during the Republican National Convention (RNC) in Cleveland, Ohio, U.S., on Thursday, July 21, 2016. This evening marks the last night of a four-day Republican National Convention that has been defined by disorderly floor activity, divisions within the party, a plagiarized speech delivered by the nominee's wife and scattered protests in the streets of Cleveland. Photographer: David Paul Morris/Bloomberg via Getty Images

CLEVELAND, OH - JULY 21: Republican presidential candidate Donald Trump preapres to deliver his speech during the evening session on the fourth day of the Republican National Convention on July 21, 2016 at the Quicken Loans Arena in Cleveland, Ohio. Republican presidential candidate Donald Trump received the number of votes needed to secure the party's nomination. An estimated 50,000 people are expected in Cleveland, including hundreds of protesters and members of the media. The four-day Republican National Convention kicked off on July 18. (Photo by Win McNamee/Getty Images)

US Republican presidential candidate Donald Trump speaks on the last day of the Republican National Convention on July 21, 2016, in Cleveland, Ohio. / AFP / Jim WATSON (Photo credit should read JIM WATSON/AFP/Getty Images)

Republican presidential candidate Donald Trump speaks on the last day of the Republican National Convention on July 21, 2016, in Cleveland, Ohio. / AFP / Robyn BECK (Photo credit should read ROBYN BECK/AFP/Getty Images)

U.S. Republican Presidential Nominee Donald Trump speaks at the Republican National Convention in Cleveland, Ohio, U.S. July 21, 2016. REUTERS/Rick Wilking

The mouth of US Republican presidential candidate Donald Trump is seen on a big screen as he speaks on the last day of the Republican National Convention on July 21, 2016, in Cleveland, Ohio. / AFP / Jim WATSON (Photo credit should read JIM WATSON/AFP/Getty Images)

CLEVELAND, OH - JULY 21: Republican presidential candidate Donald Trump delivers a speech during the evening session on the fourth day of the Republican National Convention on July 21, 2016 at the Quicken Loans Arena in Cleveland, Ohio. Republican presidential candidate Donald Trump received the number of votes needed to secure the party's nomination. An estimated 50,000 people are expected in Cleveland, including hundreds of protesters and members of the media. The four-day Republican National Convention kicked off on July 18. (Photo by John Moore/Getty Images)

US Republican presidential candidate Donald Trump speaks on the last day of the Republican National Convention on July 21, 2016, in Cleveland, Ohio. / AFP / JIM WATSON (Photo credit should read JIM WATSON/AFP/Getty Images)

A CODEPINK protester is removed while US Republican presidential candidate Donald Trump speaks on the last day of the Republican National Convention on July 21, 2016, in Cleveland, Ohio. / AFP / JIM WATSON (Photo credit should read JIM WATSON/AFP/Getty Images)

CLEVELAND, OH - JULY 21: Republican presidential candidate Donald Trump delivers a speech during the evening session on the fourth day of the Republican National Convention on July 21, 2016 at the Quicken Loans Arena in Cleveland, Ohio. Republican presidential candidate Donald Trump received the number of votes needed to secure the party's nomination. An estimated 50,000 people are expected in Cleveland, including hundreds of protesters and members of the media. The four-day Republican National Convention kicked off on July 18. (Photo by Alex Wong/Getty Images)

Republican U.S. presidential nominee Donald Trump formally accepts the nomination at the Republican National Convention in Cleveland, Ohio, U.S. July 21, 2016. REUTERS/Carlo Allegri

Republican U.S. presidential nominee Donald Trump formally accepts the nomination at the Republican National Convention in Cleveland, Ohio, U.S. July 21, 2016. REUTERS/Carlo Allegri

CLEVELAND, OH - JULY 21: Attendees listen to Republican presidential candidate Donald Trump deliver his speech on the fourth day of the Republican National Convention on July 21, 2016 at the Quicken Loans Arena in Cleveland, Ohio. Republican presidential candidate Donald Trump received the number of votes needed to secure the party's nomination. An estimated 50,000 people are expected in Cleveland, including hundreds of protesters and members of the media. The four-day Republican National Convention kicked off on July 18. (Photo by Jeff Swensen/Getty Images)

CLEVELAND, OH - JULY 21: Deligates stand and cheer as Republican presidential candidate Donald Trump delivers his speech on the fourth day of the Republican National Convention on July 21, 2016 at the Quicken Loans Arena in Cleveland, Ohio. Republican presidential candidate Donald Trump received the number of votes needed to secure the party's nomination. An estimated 50,000 people are expected in Cleveland, including hundreds of protesters and members of the media. The four-day Republican National Convention kicked off on July 18. (Photo by Win McNamee/Getty Images)

CLEVELAND, OH - JULY 21: An attendee stands and cheers as Republican presidential candidate Donald Trump delivers his speech on the fourth day of the Republican National Convention on July 21, 2016 at the Quicken Loans Arena in Cleveland, Ohio. Republican presidential candidate Donald Trump received the number of votes needed to secure the party's nomination. An estimated 50,000 people are expected in Cleveland, including hundreds of protesters and members of the media. The four-day Republican National Convention kicked off on July 18. (Photo by Chip Somodevilla/Getty Images)

Rudy Giuliani, right, former mayor of New York City, applauds as Republican Presidential Nominee Donald Trump addressed the audience during the final day of the 2016 Republican National Convention at Quicken Loans Arena in Cleveland, Ohio, July 21, 2016. (Photo by Brian van der Brug/Los Angeles Times via Getty Images)

CLEVELAND, OH - JULY 21: (L-R) Tiffany Trump, Barron Trump and Melania Trump listen to Republican presidential candidate Donald Trump deliver his speech on the fourth day of the Republican National Convention on July 21, 2016 at the Quicken Loans Arena in Cleveland, Ohio. Republican presidential candidate Donald Trump received the number of votes needed to secure the party's nomination. An estimated 50,000 people are expected in Cleveland, including hundreds of protesters and members of the media. The four-day Republican National Convention kicked off on July 18. (Photo by Jeff Swensen/Getty Images)

CLEVELAND, OH - JULY 21: Republican presidential candidate Donald Trump and his family acknowledge the crowd on the fourth day of the Republican National Convention on July 21, 2016 at the Quicken Loans Arena in Cleveland, Ohio. Republican presidential candidate Donald Trump received the number of votes needed to secure the party's nomination. An estimated 50,000 people are expected in Cleveland, including hundreds of protesters and members of the media. The four-day Republican National Convention kicked off on July 18. (Photo by Jeff Swensen/Getty Images)

US Republican presidential candidate Donald Trump (C L) and vice presidential candidate Mike Pence (C R) are joined by their families at the end of the Republican National Convention on July 21, 2016, in Cleveland, Ohio. / AFP / JIM WATSON (Photo credit should read JIM WATSON/AFP/Getty Images)

Republican presidential candidate Donald Trump embraces his wife Melania on the final night of the Republican National Convention at the Quicken Loans Arena in Cleveland, Ohio on July 21, 2016. / AFP / Jim WATSON (Photo credit should read JIM WATSON/AFP/Getty Images)

CLEVELAND, OH - JULY 21: Republican presidential candidate Donald Trump and Republican vice presidential candidate Mike Pence stand with their families on the fourth day of the Republican National Convention on July 21, 2016 at the Quicken Loans Arena in Cleveland, Ohio. Republican presidential candidate Donald Trump received the number of votes needed to secure the party's nomination. An estimated 50,000 people are expected in Cleveland, including hundreds of protesters and members of the media. The four-day Republican National Convention kicked off on July 18. (Photo by Chip Somodevilla/Getty Images)

Balloons descend on the delegates as the families of Republican presidential candidate Donald Trump and his nominee for vice-president Mike Pence appear on stage at the end of the last day of the Republican National Convention on July 21, 2016, in Cleveland, Ohio. / AFP / DOMINICK REUTER (Photo credit should read DOMINICK REUTER/AFP/Getty Images)

CLEVELAND, OH - JULY 21: Republican presidential candidate Donald Trump embraces Republican vice presidential candidate Mike Pence after his speech on the fourth day of the Republican National Convention on July 21, 2016 at the Quicken Loans Arena in Cleveland, Ohio. Republican presidential candidate Donald Trump received the number of votes needed to secure the party's nomination. An estimated 50,000 people are expected in Cleveland, including hundreds of protesters and members of the media. The four-day Republican National Convention kicked off on July 18. (Photo by Jeff J Mitchell/Getty Images)

Obama has endorsed his former secretary of state, Hillary Clinton, the Democratic nominee for president.

Obama said that even if he had lost his White House races in 2008 to McCain and in 2012 to former Massachusetts Governor Mitt Romney, he would not have doubted their abilities to lead the country.

That was not the case for Trump, a businessman from New York, Obama said.

"There has to come a point at which you say, somebody who makes those kinds of statements doesn't have the judgment, the temperament, the understanding to occupy the most powerful position in the world," Obama said.